Ciprofloxacin vs Amoxicillin: side effects in FDA adverse event reports
At a glance
| Ciprofloxacin | Amoxicillin | |
|---|---|---|
| Drug class | – | – |
| Brand names | – | – |
| FAERS reports | 96,695 | 75,882 |
| Serious | 83% | 80% |
| Death outcome | 9,728 | 5,023 |
| Boxed warning | Yes SERIOUS ADVERSE REACTIONS INCLUDING TENDINITIS, TENDON RUPTURE, PERIPHERAL NEUROPATHY, CENTRAL NERVOUS SYSTEM EFFECTS AND EXACERBATION OF MYASTHENIA GRAVIS • Fl | No |
Signals both drugs share
| Reaction | Ciprofloxacin | Amoxicillin | Label screen (A / B) |
|---|---|---|---|
| Chronic kidney disease | 4,554 · PRR 13.6 | 4,668 · PRR 17.9 | Labeled (related wording) / Not in label — unassessed |
| End stage renal disease | 1,425 · PRR 18.1 | 1,392 · PRR 22.5 | Not in label — unassessed / Not in label — unassessed |
| Tubulointerstitial nephritis | 996 · PRR 12.1 | 775 · PRR 11.9 | Not in label — unassessed / Not in label — unassessed |
| Nephrogenic anaemia | 755 · PRR 41.7 | 661 · PRR 45.4 | Not in label — unassessed / Not in label — unassessed |
| Rebound acid hypersecretion | 437 · PRR 35.9 | 440 · PRR 46.2 | Not in label — unassessed / Not in label — unassessed |
| Hyperparathyroidism secondary | 415 · PRR 42.4 | 343 · PRR 43.2 | Not in label — unassessed / Not in label — unassessed |
| Chronic sinusitis | 226 · PRR 13.9 | 272 · PRR 21.6 | Likely indication confounding / Not in label — unassessed |
| Radiculopathy | 230 · PRR 20.6 | 198 · PRR 22.4 | Not in label — unassessed / Not in label — unassessed |
| Female genital tract fistula | 246 · PRR 36.1 | 174 · PRR 31.0 | Not in label — unassessed / Not in label — unassessed |
| Proctitis | 235 · PRR 19.8 | 163 · PRR 17.0 | Not in label — unassessed / Not in label — unassessed |
| Chronic kidney disease-mineral and bone disorder | 192 · PRR 47.0 | 185 · PRR 57.3 | Not in label — unassessed / Not in label — unassessed |
| Vaginal flatulence | 177 · PRR 301.6 | 146 · PRR 254.1 | Not in label — unassessed / Not in label — unassessed |
Labeled signals distinctive to Ciprofloxacin
- Tendonitis — n=2,268, PRR 36.9 Labeled — boxed warning
- Tendon pain — n=2,035, PRR 79.7 Labeled (related wording)
- Tendon rupture — n=1,303, PRR 25.4 Labeled — boxed warning
- Tendon disorder — n=1,135, PRR 45.5 Labeled adverse reaction
- Clostridium difficile colitis — n=586, PRR 12.6 Labeled (related wording)
- Tendon injury — n=341, PRR 21.7 Labeled (related wording)
- Tendon discomfort — n=253, PRR 109.5 Labeled (related wording)
- Muscle rupture — n=235, PRR 13.9 Labeled (related wording)
Labeled signals distinctive to Amoxicillin
- Acute generalised exanthematous pustulosis — n=421, PRR 15.8 Labeled adverse reaction
- Lip oedema — n=251, PRR 17.3 Labeled (related wording)
- Meningitis aseptic — n=238, PRR 15.5 Labeled (related wording)
- Crystalluria — n=119, PRR 76.8 Labeled adverse reaction
- Enterocolitis haemorrhagic — n=103, PRR 20.5 Labeled (related wording)
- Serum sickness-like reaction — n=81, PRR 42.1 Labeled adverse reaction
Common questions
Which has more reported side effects, Ciprofloxacin or Amoxicillin?
Ciprofloxacin has 96,695 FAERS reports and Amoxicillin 75,882. More reports does not mean more dangerous: volume follows how widely and how long a drug has been used, prescription vs over-the-counter status, and publicity. The seriousness share (83% vs 80%) is a better like-for-like signal of the kind of problems reported.
Which side effects do Ciprofloxacin and Amoxicillin share?
Both drugs carry disproportionality signals for chronic kidney disease, end stage renal disease, tubulointerstitial nephritis, nephrogenic anaemia, rebound acid hypersecretion. Shared signals often reflect a shared drug class or the condition both are used for.
Is Ciprofloxacin or Amoxicillin safer?
FAERS cannot answer that: it has no denominator and no comparator. Use this page to see which risks are already on each label and which signals are unlabeled, then check the prescribing information and your clinician for your situation.
Sources: openFDA FAERS pair statistics (OpenPV build 2026-09-14), FDA labels via openFDA, openFDA count queries for seriousness and deaths. Pair chosen because it is a commonly searched comparison. Generated 2026-10-08.